This grant requests funds to purchase equipment needed for ultrastructural studies of cells and tissues. The instruments requested are: 1) A Jeolco 1200EX high resolution electron microscope with eucentric side entry goniometer with 60 degrees tilt. 2) A Balzers high vacuum chamber and accessories for coating biological specimens with heavy metal films of sufficient uniformity and thinness for high resolution scanning electron microscopy. 3) A Sorvall MT 5000 ultramicrotome. Two major user groups comprising 22 investigators, and two minor user groups comprising an additional 4 investigators are identified. The research of the investigators in the major users group is supported by 13 separate peer reviewed grants from the National Institutes of General Medical Sciences, Allergy and Infectious Diseases, Arthritis and Metabolic Diseases, Neurological and Communicative Diseases and Stroke, Cancer, Heart and Lung, and Human Development. The equipment will become part of the shared ultrastructural facilities of the Department of Physiology, and of the Department of Anatomy and Cell Biology at Columbia University, and will be used primarily by investigators working on scientific problems in three major areas: 1) Structure and interactions of blood cells, cancer cells and endothelial cells. 2) Molecular architecture and biogenesis of cellular membranes. 3) Development and function of the vertebrate nervous system. Need for this equipment is justified by the number of investigators requiring access to high resolution ultrastructural tools, the unavailability at Columbia University of high vacuum state-of-the-art heavy metal sputter coating equipment for the Jeolco 35 high resolution scanning electron microscope that is available at Columbia University, and the need for additional vibration-damped modern ultramicrotomy equipment. The equipment will be maintained by trained technical personnel and will be available 24 hours a day to a broad user group. Installation and start-up costs will be borne by Columbia University.